Apparatus for testing tensile characteristics of a material



Aug 8, 1950 A c. K. BECK ETAL 2,518,217 A APPARATUS FOR TESTING TENS'ILECHARACTERISTICS OF A MATERIAL Filed July 3, 1945 lNVENTOR curFoRn x.BECK DAVID KIRKPATRICK Y E N R O n A Patented Aug. 8, 1950 UNITED STATEs PATENT OFFICE Application July 3, 1945, serial No. 603,089

4 Claims. (01. 72-153) This invention relates to .inechanical testingapparatus and more particularly to improved apparatus for determiningthe tensile properties of a material at a controlled temperature.

In determining the characteristics oi metals that are to be used forstructural and other 'puroses it is frequently desirable to measure thetensile characteristics of the metal. such as tensile strength, elasticlimit, elastic modulus and the like. These characteristics vary withtemp'erature and in cases where the metal is to be stressed at anelevated or depres'sed temperature it is sometimes desirable that thetest piece be maintained at a redeterminedand corresponding' temperaturewhile its tensile characteristics are beingmeasured.

.Itis accordingly anobject of the present invem tion to provide improvedapparatus for testing the tensile characteristics of a material at atemperature other than atmospheric temperature. i

It is a further object of the invention to provide such tensile testingapparatus wherein'thc test piece is uniformly maintained at a prede-itermined desired temperature while it is being stressed. r

It is still another object of the invention to provide tensile testingapparatus of this character wherein the temperature of the test piece iseasily, ra idly and accurately controllable.

,Other objects of the invention will be in part obvious and in partpointed out hereinafter.

The many objects and advantages of the present invention may be bestunderstood by reference to the accompanying drawing which shows atensile tester incorporating a preferred embodimerit of the presentinvention. Referring to the drawing the numeral in designates a glasscasing which is sup orted by the clamps it that are in turn fixed to atrams [4 comprising the vertical standards l6 and cross-bar [8.Supported from the cross-bar l8 and suspended within the transparentcasing Ill there is a strip 20 of the material to be tested. At itsupper end the strip 26 passes through a close-fitting hole 22 in the topof casing l6 and is held in a clamp 24 supported by a ring 26 which isin turn supported on the horizontal bar iii of the frame I4. At itslower end the test strip 20 passes through a closefitting hole 28 in thebottom of the casing I and is held in a clamp 30 on which is suspended aplurality of weights 32. On the face of the test strip 20 within thecasing I0 there is a reference scale 34 which is adapted to cooperatewith a. fixed reference mark outside the casing III, for

example, a reference mark in a micrometer microscope (not shown), toindicate the elongas tion of the strip when a predetermined weight 33 issuspended therefrom. Thus by suspending predetermined different weightsfrom the clamps ill-and observing the movement of the reference scale 34the elongation of the strip 2!.) for a given applied stress may bedetermined. v

As pointed out above it is sometimes desirable to determine the tensilecharacteristics of a test piece at a predetermined constant or variabletemperature other than atmospheric tempera.- ture and in the presentconstruction means are, provided for attaining this objective. Extend!-ing from the side of the casing In at a point approximately midwaybetween the ends of the casing there is a heating chamber 36 containinga heating element 38 which may be supplied with electrical energy fromany suitable source (not shown). A heating gas such as air is suppliedthrough a supply pipe 46 and flows through branch pipes 42 and 44 intothe upwardly and downwardly extending arms 45 and 46 of the heatingchamber 36l The air then flows through the heatingchamber 36,, where itis heated, to the interior ofthe casing ll! where it flows over the teststrip '28 to heat the strip to the desired. temperature. The heated airfirst comes in contact with the test strip 20 about the middle there ofand flows in opposite directions along the strip and out through the endholes .22 and 28 of the casing. The temperature of the heating gases andtherefore of the strip is measured by the thermometers 4B and 50 locatedin the upper and lower portions of the casing l0 respectively.

In order to maintain a, more nearly uniform temperature within thecasing It! a portion of the heating air entering the casing isrecircwlated. Interconnecting the upper portion of caslog in and theupper arm 45 of the heating chamber 36 there is a conduit 52 and asimilar conduit 54 interconnects the lower portion of casing H] with thearm 46. The pipes 42 and 44- preferably extend well into the arms 45 and46 respectively and the ends of the pipes are formed into the jets 56and 58. Thefiow of air through jet 56 causes air to be drawn from thetop of casing In through conduit 52 in a well known manner to produce acirculation of gas through the heating chamber 36, casing Ill, conduit52 and arm 45. In a similar manner the flow of air through jet 58produces circulation of air through heating chamber 36, casing It,conduit 54 and arm 46. The flow of air through the pipes 42 and M isregulated by adjustment of valves 60 and 62. l

From the above description it is apparent that the present inventioncomprises a compact and efficient structure for testing the tensileproperties of a material at a controlled temperature. The apparatus hasbeen found particularly useful in testing the tensile properties ofrelatively fragile materials, for example finely porous, permeablemembrances to be used in separating gases by diffusion at temperaturesabove atmospheric temperature. The jets 56 and 58 produce effectivecirculation of the heating gas thus ensuring uniformity of temperatureand the temperature may be easily and accurately controlled either byadjusting the heating energy supply to the heating element 38 or byadjustment of the control valves 60 and 62.

It is of course to be understood that the invention isjnot limited tothe specific details described above. Thus if it is desired that thetensile properties of a test piece be measured at a temperature belowthat of the atmosphere a suitable refrigerator may be sub tituted forthe heating chamber 36. Other variations'within the scone of theinvention will occur to those skilled in the art.

' We claim:

1. In apparatus for measuring the tensile properties of a material, incombination, a test chamber. means for supporting a test piece of saidmat rial within said test chamber, tensioning means for applying tensionto said test piece, gas supply means for continuously supplying a heatedgas to said chamber at a point near the center of said test piece tocause a stream of said gas to flow over said test piece in oppositedirections toward the ends of said piece, and means for 3. In apparatusfor measuring the tensile properties of a material, in combination, atest chamber, means for supporting a test piece of said material withinsaid test chamber, tensioning means for applying tension to said testpiece, a pair of fluid supply conduits for conducting a heated fluid toa point near the center of said test chamber to cause said heated fluidto flow over said test piece in opposite directions toward the ends ofsaid test piece, each of said fluid conduits being provided with a fluidjet, a pair of fluid return conduits connected at one end of each ofsaid return conduits to said test chamher at points spaced oppositelyfrom the point to which said fluid is admitted to said chamber, theopposite end of each of said return conduits being connectedrespectively one to each of said supply conduits adjacent saidjetstocause said withdrawing gas from said chamber at points s acedaxially of the chamber at opposite sides of the point where said gas isadmitted to said chamber. n j

2. In apparatus for measuring the tensile properties of a material, incombination, a test chamber, means for supporting a test piece of saidmaterial within said test chamber, tensioning means for applying tensionto said test piece, a fluid sup ly conduit for supplying a heated fluidto said test chamber to cause said fluid to flow over said test pieceand maintain said test piece at a predetermined desired temperature,said supply conduit including a fluid jet, a fluid return conduitconnected to said supply conduit at a point near said jet and to saidtest chamber at a point spaced from said supply conduit to cause saidjet to produce a circulatory flow of said heated fluid within said testchamber, said test chamber being provided with an opening through whicha portion of the fluid can escape from the apparatus.

jets to produce circulatory flow of said heated fluid within said .testchamber, .and said test chamber being provided with an opening throughwhich a portion of said fluid can escape from the apparatus. f

4. Apparatus for measuring the tensile properties of a materialcomprising a test chamber, means for supporting a test piece of saidma-' terial within said test chamber, means for applying tension to saidtest piece, a source of gas under pressure, a gas conduit connected tosaid source and terminating in a jet, gas temperature adjusting meansdisposed to receive gas from said jet and toadust the temperature of thegas, a conduit connecting said temperature adlusting means and saidtestchamber to conduct gas at the adjusted temperature into said cham her toflow over said test piece, and a gas return conduit connected to saidtest chamber and to said temperature adjusting means, the pointofconnection of the said return conduit and said temperature adjustingmeans being adjacent said jet whereby the operation of the jet produces"a region of 10w pressure causing the flowof gas through said returnconduit from said test cham her to said temperature adjusting means,said test' chamber being provided with an opening through which aportion of said gas can escape.

' CLIFFORD K. BECK.

DAVID KIRKPATRICK.

' REFERENCES CITED The following references are of record the file ofthis patent:

UNITED STATES- PATENTS Semchyshen May 1, 1945

